Motorized vehicles in which a front wheel and a rear wheel are situated in succession, and which are therefore single-tracked, are referred to as two-wheeled motor vehicles, sometimes also as motorcycles. Such single-track vehicles are particularly susceptible to accidents due to their ability to tilt laterally, transversely with respect to the travel direction. It is therefore desirable to recognize critical driving situations early that may result in the two-wheeled vehicle tipping over and thus having a dangerous accident, and to avoid or counteract them or mitigate their consequences.
A frequent cause of accidents with motorized two-wheeled vehicles when negotiating curves, without the involvement of other vehicles, is excessive over- or understeering of the vehicle with lateral skidding of one or both wheels. These situations are caused primarily by excessive curve speeds, excessive acceleration or braking in an inclined position, or by a roadway section with a low friction coefficient between the tires and the roadway, i.e., a so-called low-μ patch. In particular the latter-mentioned case is feared even by experienced motorcyclists.
Extremely effective systems for preventing excessive over- or understeering for two-track vehicles have become widespread in the market, such as vehicle dynamics control systems such as the electronic stability program (ESP®). Instability is recognized by observing a rider intent (setpoint yaw rate, computed from the steering angle) and an actual vehicle response (actual yaw rate). There are also similar strategies with the observation of an estimated sideslip angle β and a wheel slip angle α that is computed from same. When there are distinct differences between setpoint and actual values, corrective measures may be taken via engine and braking interventions.
The driving dynamics are much more demanding for single-track two-wheeled motor vehicles than for two-track passenger vehicles. For example, roll angles Φ are typically in the range of ±50°, while generally smaller roll angles of ±7° occur with recent two-track vehicles. In addition to the demanding driving dynamics, the consequences of exceeding the physical limits are often serious. Thus, even brief instabilities, for example due to a low-μ patch, sometimes result in severe accidents for two-wheeled motor vehicles. A passenger vehicle would only briefly slide or move slightly laterally.
Against the background of comparatively high accident rates, efforts have therefore also been made for two-wheeled motor vehicles, using improved sensor systems and estimation algorithms that make driving dynamics functions for braking and acceleration, which are already present, suitable for negotiating curves. An estimation algorithm for ascertaining the motorcycle sideslip angle and computing the front and rear wheel slip angles for two-wheeled motor vehicles that is thus made possible is currently being developed for mass production.